In article ,
Bryan wrote:
:I have a Mercruiser Alpha One carbureted 6 cyl 190 hp motor on my boat.
:Should I expect the boat to run normally at Lake Tahoe or will it need a
:tune up each time I visit Lake Tahoe from sea level?
:I've been told I don't need to alter the tuning if I switch props to one
:with more torque when I visit Tahoe.

You will defintely lose power up here (I live in South Lake Tahoe). I
have and use two props...a 15x15 for sea level and lower elevation
(below about 4000') and a 15x17 for use in Tahoe. If I were to use the
15x15 prop in Tahoe, I would never reach my engine's WOT RPM spec.
Even when the correct prop is used, I lose about 20-25% power up here
as compared to sea level. My boat, a 17' runabout v-hull with a little
4 cylinder 130 hp Volvo AQ130C in it, goes from 32-33 mph WOT at sea
level down to about 27 mph WOT in Tahoe...and that is with the prop
change. I don't do any tuning for high elevation...I know you could
advance the timing slightly to improve performance a bit, but I don't,
and I don't think there is anything else I could do that would impact
high speed operation on this engine...if there is anything besides
that, I'd like to know about it.